Perinatal transmission of HIV infection is a problem of increasing concern and magnitude. In New York City 2.0 - 3.5% of pregnant women delivering in municipal hospitals are infected with HIV. This study, performed at a single institution, has assembled multidisciplinary team to study perinatal transmission of HIV and the natural history of HIV infection in infants. Women with (1) a history of drug use, (2) with sex partners who are drug users or (3) of Haitian origin are enrolled during pregnancy at which time a detailed 45 minute interview is administered and blood is drawn for serological, immunologic and where appropriate virologic studies. Women are seen a second time prior to delivery where additional information and blood samples are collected. AT birth child and mother are again examined and blood samples drawn. Mother and child are then followed and data and blood collected every month for 6 months and every 3 months thereafter. Clinical and neurologic evaluations, serologic (including new antigen or IgM assays) immunologic, and virological data, are correlated with the outcome. The long range goals are to define the rate of HIV transmission, the predictors of transmission n the mother, factors that may influence transmission (e.g. HTLV-I, drug use), natural history of perinatally acquire infection, neurodevelopmental impact of HIV on infants, factors that influence disease expression in infants, and to aid in the development of tests that predict whether an asymptomatic HIV positive infant is infected. Long term follow-up of this closely studied cohort of seropositive and matched seronegative women and their infants, combined with an extensive network of basic science collaborators should help us achieve our long term goals. The inclusion of a significant number of cases of perinatally acquired disease in non-drug users will also aid us in the study the impact of HIV disease, vs. HIV disease and drugs, vis. drugs alone, on infants.